This invention relates generally to air valves and more particularly to air valves designed to minimize icing and improve efficiency for a diaphragm pump or the like.
This invention relates to an improved fluid operated, double diaphragm pump, and, more particularly, to the pilot valve construction for such a pump.
The use of a double diaphragm pump to transfer materials is known. Typically such a pump comprises a pair of pumping chambers with a pressure chamber arranged in parallel with each pumping chamber in a housing. Each pressure chamber is separated from its associated pumping chamber by a flexible diaphragm. As one pressure chamber is pressurized, it forces the diaphragm to compress fluid in the associate pumping chamber. The fluid is thus forced from the pumping chamber. Simultaneously, the diaphragm associated with the second pumping chamber is flexed so as to draw fluid material into the second pumping chamber. The diaphragms are reciprocated in unison in order to alternately fill and evacuate the pumping chambers. In practice, the chambers are all aligned so that the diaphragms can reciprocate axially in unison. In this manner the diaphragms may also be mechanically interconnected to ensure uniform operation and performance by the double acting diaphragm pump.
Various controls have been proposed as the major distribution valve for providing a pressurized motive fluid, e.g., pressurized air, to the chambers associated with the double acting diaphragm pump. An exemplary control is shown in commonly assigned U.S. Pat. No. 4,854,832, in which a double diaphragm pump has a major distribution valve which includes a spool actuator that receives a sliding xe2x80x9cDxe2x80x9d valve. The spool actuator has a series of different diameters so as to provide for actuation is response to pressure differential thereby shifting the xe2x80x9cDxe2x80x9d valve between passageways to fill and exhaust the air chambers that drive the pump.
In designing air motor valving used to control the feed air to and exhaust air from the diaphragm chambers of such pumps, however, it is desirable to exhaust the diaphragm chambers as quickly as possible in order to obtain a fast switch over and high average output pressures. To achieve rapid exhaust times, larger distribution valves such as a elastomer-fitted or close fit spool-type valves are typically provided having larger porting that permits the rapid exhausting of air. Large temperature drops are generated with these larger valves, however, which cause the valve to become extremely cold and can cause ice formation from moisture in the exhaust air.
In order to minimize icing and improve the efficiency of the pump, commonly assigned U.S. Pat. No. 5,584,666, discloses a diaphragm pump having air valves designed to divert cold exhaust air from the major distribution valve. These air valves are bypass check valves, also known as xe2x80x9cquick dumpxe2x80x9d valves, which are used in conjunction with spool valves due to their ability to pass large volumes of air in a relatively small package.
However, spool-type valves consist of many parts, which include rubber seals, or can be of the type which use close or lap fits to eliminate the elastomeric seals. Elastomer-fitted spools function well in dirty wet air and will not leak air when the pump stalled against backpressure. The elastomers used in an elastomer-fitted spool, however, are susceptible to chemical attack from airborne lubricants, which can cause the valve to hang up or stick. The lapped or close-fit spools eliminate parts but typically require constant lubrication to prevent sticking and do not function well with dirty air. Because there also must be some clearance between the spool and housing, air leakage will occur when the pump is stalled against backpressure, thus wasting compressed air.
The foregoing illustrates limitations known to exist in present devices and methods. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.
In one aspect of the present invention this is accomplished by providing a reduced icing valve for a gas-driven motor and a reciprocating double diaphragm pump having a shiftable valve for alternatively supplying a motive gas through first and second supply ports to opposed first and second power pistons in opposed motive gas chambers, respectively, and for effecting alternating exhaust of the chambers. The shiftable valve is provided with an insert that deflects, away from the shiftable valve, air entering from each of the bypass valves until the bypass valves are fully actuated by the exhaust gas from the motive gas chambers. The shiftable valve is further provided with bypass valves independent of and intermediate the shiftable valve and each of the first and second motive gas chambers for bypassing the shiftable valve by exhaust gas from the motive gas chambers. The bypass valves are further actuated in an opposing direction by a supply source of motive gas to the chambers.